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Electrical Safety

Electrical Safety. How the human body works . The brain sends electrical signals through the spinal cord/nerves to the muscles These very small amounts of current cause our muscles to expand and contract One of the muscles that is controlled is the Heart. Human Reactions to Electric Current.

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Electrical Safety

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  1. Electrical Safety

  2. How the human body works • The brain sends electrical signals through the spinal cord/nerves to the muscles • These very small amounts of current cause our muscles to expand and contract • One of the muscles that is controlled is the Heart

  3. Human Reactions to Electric Current Current can cause skin to burn, muscles to freeze and hearts to fibrillate

  4. Negative Application of Electricity and the Body • If 0.1 A (AC) of current is applied, fibrillation occurs • This involves a rapid, uncontrollable twitching of the heart • This prevents circulation and if not stopped, will result in death

  5. Negative Application of Electricity and the Body • Let-go Threshold • At 0.02 A (AC) your muscles become paralyzed • The electrical signal from your brain cannot overcome the external electrical signal and your muscles stay contracted • This also means, you cannot let go of whatever you are being electrocuted by

  6. Let Go Threshold in Action • Taser Scene – The Hangover • Taser Scene – Marine Tough • In these clips, when people are hit be a taser, the current applied overwhelms their bodies ability to control muscles.

  7. Positive Application of Electricity and the Body • Defibrillators • Applies a large current throughout the body • Restores fibrillating heart (possibly due to heart attack) to normal heartbeat

  8. How a defibrillator works! • Using a defibrillator to restore normal heart function

  9. Being Defibrillated • The process of using a defibrilator • A scene from House

  10. Positive Application of Electricity and the Body • Pace Makers • If a person does not produce a regular heart beat, a pace maker is installed to stimulate heart muscle cells to produce a regular pumping rate • The pace maker applies regular electrical shocks to the heart

  11. Pacemaker Implantation • How a pacemaker works

  12. Why don’t you stand in a bath tub with a hair dryer? • Moisture can greatly affect resistance • Dry Person – 106Ω • Person with wet skin – 1500 Ω • Person sitting in bath water – 500 Ω • If exposed to 120 V (AC), current is: • Dry Person – 0.00012 A – Very Unpleasant • Person with wet skin – 0.08 A - Fatal • Person sitting in bath water – 0.24 A - Fatal

  13. How do we protect ourselves? • We use fuses • A fuse detects a change in current due to short circuit or electrocution and breaks the circuit • Household dangers • Overloaded circuit – draws too much current and results in an overheated circuit, risk of fire • Short circuit – there is no load in a circuit and the circuit can overheat

  14. Homework • Complete Pg 348 # 3,4 & Pg 350 # 2,3 (note: a 7.0-A extension cord can only hold 7.0A of current before posing a fire risk)

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